Silicate compounds as solid Li-ion conductors

ABSTRACT

Solid-state lithium ion electrolytes of lithium silicate based composites are provided which contain an anionic framework capable of conducting lithium ions. An activation energy for lithium ion migration in the solid state lithium ion electrolytes is 0.5 eV or less and room temperature conductivities are greater than 100.5 S/cm. Composites of specific formulae are provided and methods to alter the composite materials with inclusion of aliovalent ions shown. Lithium batteries containing the composite lithium ion electrolytes are also provided.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of prior U.S. applicationSer. No. 16/013,495, filed Jun. 20, 2018, the disclosure of which isincorporated herein by reference in its entirety.

BACKGROUND

Li-ion batteries have traditionally dominated the market of portableelectronic devices. However, conventional Li-ion batteries containflammable organic solvents as components of the electrolyte and thisflammability is the basis of a safety risk which is of concern and couldlimit or prevent the use of Li-ion batteries for application in largescale energy storage.

Replacing the flammable organic liquid electrolyte with a solidLi-conductive phase would alleviate this safety issue, and may provideadditional advantages such as improved mechanical and thermal stability.A primary function of the solid Li-conductive phase, usually calledsolid Li-ion conductor or solid state electrolyte, is to conduct Li⁺ions from the anode side to the cathode side during discharge and fromthe cathode side to the anode side during charge while blocking thedirect transport of electrons between electrodes within the battery.

Moreover, lithium batteries constructed with nonaqueous electrolytes areknown to form dendritic lithium metal structures projecting from theanode to the cathode over repeated discharge and charge cycles. If andwhen such a dendrite structure projects to the cathode and shorts thebattery energy is rapidly released and may initiate ignition of theorganic solvent.

Therefore, there is much interest and effort focused on the discovery ofnew solid Li-ion conducting materials which would lead to an all solidstate lithium battery. Studies in the past decades have focused mainlyon ionically conducting oxides such as for example, LISICON(Li₁₄ZnGe₄O₁₆), NASICON(L_(1.3)Al_(0.3)Ti_(1.7)(PO₄)₃), perovskite (forexample, La_(0.5)Li_(0.5)TiO₃), garnet (Li₇La₃Zr₂O₁₂), LiPON (forexample, Li_(2.88)PO_(3.73)N_(0.14)) and sulfides, such as, for example,Li₃PS₄, Li₇P₃dS₁₁ and LGPS (Li₁₀GeP₂S₁₂).

While recent developments have marked the conductivity of solid Li-ionconductor to the level of 1-10 mS/cm, which is comparable to that inliquid phase electrolyte, finding new Li-ion solid state conductors isof great interest.

An effective lithium ion solid-state conductor will have a high Li⁺conductivity at room temperature. Generally, the Li⁺ conductivity shouldbe no less than 10⁻⁶ S/cm. Further, the activation energy of Li⁺migration in the conductor must be low for use over a range of operationtemperatures that might be encountered in the environment. Additionally,the material should have good stability against chemical,electrochemical and thermal degradation. Unlike many conventionallyemployed non-aqueous solvents, the solid-state conductor material shouldbe stable to electrochemical degradation reactivity with the anode andcathode chemical composition. The material should have low grainboundary resistance for usage in an all solid-state battery. Ideally,the synthesis of the material should be easy and the cost should not behigh. Unfortunately, none of the currently known lithium ion solidelectrolytes meet all these criteria. For example, Li₁₀GeP₂S₁₂ fails tomeet the requirement of electrochemical stability and has a high costdue to the presence of Ge, despite its state-of-art Li conductivity.Environmentally stable composite materials having high Li⁺ conductivityand low activation energy would be sought in order to facilitatemanufacturing methods and structure of the battery.

The standard redox potential of Li/Li+ is −3.04 V, making lithium metalone of the strongest reducing agent available. Consequently, Li metalcan reduce most known cationic species to a lower oxidation state.Because of this strong reducing capability when the lithium metal of ananode contacts a solid-state Li⁺ conductor containing cation componentsdifferent from lithium ion, the lithium reduces the cation specie to alower oxidation state and deteriorates the solid-state conductor.

For example, the conductor of formula:Li₃PS₄contains P⁵⁺ in the formula and is thus a secondary cation to the Li⁺.When in contact with Li metal, reduction according to the followingequation occurs (J. Mater. Chem. A, 2016, 4, 3253-3266).Li₃PS₄+5Li→P+4Li₂SP+3Li→Li₃P

Similarly, Li₁₀GeP₂S₁₂ has also been reported to undergo degradationwhen in contact with lithium metal according to the following equations(J. Mater. Chem. A, 2016, 4, 3253-3266):Li₁₀GeP₂S₁₂+10Li→2P+8Li₂S+Li₄GeS₄P+3Li→Li₃P4Li₄GeS₄+31 Li→16Li₂S+Li₁₅Ge₄Li₁₀GeP₂S₁₂ contains Ge⁴⁺ and P⁵⁺ and each is reduced as indicated.

In another example, Li₇La₃Zr₂O₁₂, which contains secondary cations La³⁺and Zr⁴⁺ undergoes chemical degradation when in contact with lithiummetal according to the following chemistry (J. Mater. Chem. A, 2016, 4,3253-3266):6Li₇La₃Zr_(z)O₁₂+40Li→4Zr₃O+41Li₂O+9La₂O₃Zr₃O+2Li→Li₂O+3ZrLa₂O₃+6Li→2La+3Li₂O

Thus, many current conventionally known solid Li-ion conductors suffer astability issue when in contact with a Li metal anode.

The inventors of this application have been studying lithium compositecompounds which may serve for future use of solid-state Li+ conductorsand previous results of this study are disclosed in U.S. applicationSer. No. 15/626,696, filed Jun. 19, 2017, and U.S. Ser. No. 15/805,672,filed Nov. 7, 2017. However, composites of highest efficiency, higheststability, low cost and ease of handling and manufacture continue to besought.

Accordingly, an object of this application is to identify a range offurther materials having high Li ion conductivity while being poorelectron conductors which are suitable as a solid state electrolyte fora lithium ion battery.

A further object of this application is to provide a solid state lithiumion battery containing a solid state Li ion electrolyte membrane.

SUMMARY OF THE EMBODIMENTS

These and other objects are provided by the embodiments of the presentapplication, the first embodiment of which includes a solid-statelithium ion electrolyte, comprising: a composite material of formula(I):Li_(y)(M1)_(x1)Si_(2-x2)(M2)_(x2)O₇  (I)

wherein x1 is a number from 0 to 6 inclusive of 0 and 6, x2 is a numberfrom 0 to 2, inclusive of 0 and 2, and y is a value such that thecomposite of formula (I) is charge neutral, M1 is at least one elementselected from the group of elements consisting of a group 1 element, agroup 2 element and a group 12 element, and M2 is at least one elementselected from the group of elements consisting of a group 13 element, agroup 14 element, and a group 15 element.

In an aspect of the first embodiment a lithium ion (Li⁺) conductivity ofthe solid state lithium ion electrolyte is at least 10⁻⁵ S/cm at 300K.

In another aspect of the first embodiment an activation energy of thecomposite of formula (I) is 0.4 eV or less.

In a further aspect of the first embodiment, the composite of formula(I) comprises a crystal lattice structure having a tetragonal unit cell.

In a special aspect of the first embodiment the composite of formula (I)is a material of formula (Ia):Li₆Si₂O₇  (Ia).

In a second embodiment, a solid-state lithium ion electrolyte,comprising:

a composite material of formula (II) is provided:Li_(y)(M1)_(x1)Si_(2-x2)d(M2)_(x2)Pb_(1-x3)(M3)_(x3)O₇  (II)

wherein

x1 is a number from 0 to 10 inclusive of 0 and 10, x2 is a number from 0to 2, inclusive of 0 and 2, x3 is a number from 0 to 1, inclusive of 0and 1, and y is a value such that the composite of formula (II) ischarge neutral, M1 is at least one element selected from the group ofelements consisting of a group 1 element, a group 2 element and a group12 element, M2 is at least one element selected from the group ofelements consisting of a group 13 element, a group 14 element, and agroup 15 element, and M3 is at least one element selected from a group 2element, a group 12 element, a group 13 element, a group 14 element anda group 15 element.

In an aspect of the second embodiment a lithium ion (Li⁺) conductivityof the solid state lithium ion electrolyte is at least 10⁻⁵ S/cm at300K.

In another aspect of the second embodiment an activation energy of thecomposite of formula (II) is 0.45 eV or less.

In a further aspect of the second embodiment, the composite of formula(II) comprises a crystal lattice structure having a monoclinic unitcell.

In a special aspect of the first embodiment the composite of formula(II) is a material of formula (IIa):Li₁₀Si₂PbO₁₀  (IIa).

In a third embodiment, a solid-state lithium ion electrolyte,comprising:

a composite material of formula (III) is provided:Li_(y)(M1)_(x1)Si_(2-x2)(M2)_(x2)Al_(1-x3)(M3)_(x3)O₇  (III)

-   -   wherein    -   x1 is from 0 to 1, inclusive of 0 and 1, x2 is from 0 to 1,        inclusive of 0 and 1, x3 is from 0 to 1, inclusive of 0 and 1,        and y is a value such that the composite of formula (III) is        charge 10 neutral, M1 is at least one element selected from a        group 1 element, a group 2 element and a group 12 element, M2 is        at least one element selected from a group 13 element, a group        14 element, and a group 15 element, and M3 is at least one        element selected from a group 3 element, a group 4 element, a        group 13 element, a group 14 element and a group 15 element.

In an aspect of the third embodiment a lithium ion (Li⁺) conductivity ofthe solid state lithium ion electrolyte is at least 10⁻⁶ S/cm at 300K.

In another aspect of the third embodiment an activation energy of thecomposite of formula (I) is 0.40 eV or less.

In a further aspect of the third embodiment, the composite of formula(III) comprises a crystal lattice structure having a trigonal unit cell.

In a special aspect of the third embodiment the composite of formula(III) is a material of formula (IIIa):LiAlSiO₄  (IIIa).

In a further special aspect of thr third embodiment the composite offormula (III) is the material of formula (IIIb):Li_(1.33)Al_(1.33)Si_(0.67)O₄  (IIIb).

In a fourth embodiment a solid-state lithium ion electrolyte,comprising:

a composite material of formula (IV) is provided:Li_(y)(M1)_(x1) Si_(2-x2)(M2)_(x2)Be_(1-x3)(M3)_(x3)O₇  (IV)

wherein x1 is from 0 to 2, inclusive of 0 and 2, x2 is from 0 to 1,inclusive of 0 and 1, x3 is from 0 to 1, inclusive of 0 and 1, and y isa value such that the composite of formula (IV) is charge neutral, M1 isat least one element selected from the group of elements consisting of agroup 1 element, a group 2 element and a group 12 element, M2 is atleast one element selected from a group 13 element, a group 14 element,and a group 15 element, and M3 is at least one element selected from agroup 1 element, a group 2 element, a group 12 element and a group 13element.

In an aspect of the fourth embodiment a lithium ion (Li⁺) conductivityof the solid state lithium ion electrolyte is at least 10⁻⁶ S/cm at300K.

In another aspect of the fourth embodiment an activation energy of thecomposite of formula (I) is 0.40 eV or less.

In a further aspect of the fourth embodiment, the composite of formula(IV) comprises a crystal lattice structure having an orthorhombic unitcell.

In a special aspect of the fourth embodiment the composite of formula(IV) is a material of formula (IVa):Li₂BeSiO₄  (IVa).

In a fifth embodiment, a solid-state lithium ion electrolyte,comprising:

a composite material of formula (V) is provided:Li_(2.4)Zn_(4.4)Si_(5.2)O₁₆  (V).

In a sixth embodiment a solid state lithium battery is included. Thesolid state lithium battery comprises: an anode; a cathode; and a solidstate lithium ion electrolyte located between the anode and the cathode;wherein the solid state lithium ion electrolyte comprises a compositematerial according to any of the above described five embodiments andaspects thereof.

The foregoing description is intended to provide a general introductionand summary of the present disclosure and is not intended to be limitingin its disclosure unless otherwise explicitly stated. The presentlypreferred embodiments, together with further advantages, will be bestunderstood by reference to the following detailed description taken inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the Office upon request and paymentof the necessary fee.

FIG. 1 shows the crystal structure of Li₆Si₂O₇.

FIG. 2 shows the XRD analysis of the crystal structure of Li₆Si₂O₇.

FIG. 3 shows a table listing the peak positions and intensity for peaksof relative intensity of 1 or greater compared to the peak of greatestintensity in the XRD analysis of Li₆Si₂O₇ in FIG. 2 .

FIG. 4 shows the crystal structure of Li₁₀Si₂PbO₁₀.

FIG. 5 shows the XRD analysis of the crystal structure of Li₁₀Si₂Pb₁₀.

FIG. 6 shows a table listing the peak positions and intensity for peaksof relative intensity of 1 or greater compared to the peak of greatestintensity in the XRD analysis of FIG. 5 .

FIG. 7 shows the crystal structure of LiAlSiO₄.

FIG. 8 shows the XRD analysis of the crystal structure of LiAlSiO₄.

FIG. 9 shows a table listing the peak positions and intensity for peaksof relative intensity of 1 or greater compared to the peak of greatestintensity in the XRD analysis of FIG. 8 .

FIG. 10 shows the crystal structure of Li₂BeSiO₄.

FIG. 11 shows the XRD analysis of the crystal structure of Li₂BeSiO₄.

FIG. 12 shows a table listing the peak positions and intensity for peaksof relative intensity of 1 or greater compared to the peak of greatestintensity in the XRD analysis of FIG. 11 .

FIG. 13 shows the crystal structure of Li_(2.4)Zn_(4.4)Si_(5.2)∘₁₆.

FIG. 14 shows the XRD analysis of the crystal structure ofLi_(2.4)Zn_(4.4)Si_(5.2)◯₁₆.

FIG. 15 shows a table listing the peak positions and intensity for peaksof relative intensity of 1 or greater compared to the peak of greatestintensity in the XRD analysis of FIG. 14 .

FIG. 16 shows an Arrhenius plot of Li⁺ diffusivity (D) in Li₁₀Si₂PbO₁₀and Li₆Si₂O₇.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Throughout this description, the terms “electrochemical cell” and“battery” may be employed interchangeably unless the context of thedescription clearly distinguishes an electrochemical cell from abattery. Further the terms “solid-state electrolyte” and “solid-stateion conductor” may be employed interchangeably unless explicitlyspecified differently.

Structural characteristics of effective Li⁺ conducting crystal latticeshave been described by Ceder et al. (Nature Materials, 14, 2015,1026-1031) in regard to known Li⁺ ion conductors Li₁₀GeP₂S₁₂ andLi₇P₃S₁₁, where the sulfur sublattice of both materials was shown tovery closely match a bcc lattice structure. Further, Li⁺ ion hoppingacross adjacent tetrahedral coordinated Li⁺ lattice sites was indicatedto offer a path of lowest activation energy.

The inventors are conducting ongoing investigations of new lithiumcomposite compounds in order to identify materials having the propertieswhich may serve as solid-state electrolytes in solid state lithiumbatteries. In the course of this ongoing study and effort the inventorshave developed and implemented a methodology to identify compositematerials which have chemical and structural properties which have beendetermined by the inventors as indicators of lithium ion conductancesuitable to be a solid state electrolyte for a lithium-ion battery.

To qualify as solid state electrolyte in practical applications, thematerial must meet several certain criteria. First, it should exhibitdesirable Li-ion conductivity, usually no less than 10⁻⁶ S/cm at roomtemperature. Second, the material should have good stability againstchemical, electrochemical and thermal degradation. Third, the materialshould have low grain boundary resistance for usage in all solid-statebattery. Fourth, the synthesis of the material should be easy and thecost should not be high.

A criterion of this methodology requires that to qualify as solid stateelectrolyte in practical application, the material must exhibitdesirable Li-ion conductivity, usually no less than 10⁻⁶ S/cm at roomtemperature. Thus, ab initio molecular dynamics simulation studies wereapplied to calculate the diffusivity of Li ion in the lattice structuresof selected silicate materials. In order to accelerate the simulation,the calculation was performed at high temperatures and the effect ofexcess Li or Li vacancy was considered. In order to create excess Li orLi vacancy, aliovalent replacement of cation or anions may be evaluated.Thus, Li vacancy was created by, for example, partially substituting Siwith aliovalent cationic species while compensating the chargeneutrality with Li vacancy or excess Li. For example, replacing 50% ofSi in Li₁₀Si₂PbO₁₀ with P results in the formation of Li₉PSiPbO₁₀.

The diffusivity at 300 K was determined according to equation (1)D=D₀exp(−E_(a)/k_(b)T)  equation (1)where D₀, E_(a) and k_(b) are the pre-exponential factor, activationenergy and Boltzmann constant, respectively. The conductivity is relatedwith the calculated diffusivity according to equation (II):σ=D₃₀₀ρe²/k_(b)T  equation (11)where ρ is the volumetric density of Li ion and e is the unit charge.

The anionic lattice of Li-ion conductors has been shown to match certainlattice types (see Nature Materials, 14, 2015, 2016). Therefore, in theanionic lattice of the potential Li⁺ ion conductor is compared to theanionic lattice of Li⁺ ion conductor known to have high conductivity.

Thus, selected lithium silicate compounds were compared to Li-containingcompounds reported in the inorganic crystal structure database (FIZKarlsruhe ICSD—https://icsd.fiz-karlsruhe.de) and evaluated incomparison according to an anionic lattice matching method developed bythe inventors for this purpose and described in copending U.S.application Ser. No. 15/597,651, filed May 17, 2017, to match thelattice of these compounds to known Li-ion conductors.

According to the anionic lattice matching method described in copendingU.S. application Ser. No. 15/597,651, an atomic coordinate set for thecompound lattice structure may be converted to a coordinate set for onlythe anion lattice. The anions of the lattice are substituted with theanion of the comparison material and the obtained unit cell rescaled.The x-ray diffraction data for modified anion-only lattice may besimulated and an n×2 matrix generated from the simulated diffractiondata. Quantitative structural similarity values can be derived from then×2 matrices.

The purpose of anionic lattice matching is to further identify compoundswith greatest potential to exhibit high Li⁺ conductivity. From thiswork, the compounds described in the embodiments which follow weredetermined to be potentially suitable as a solid-state Li⁺ conductors.

Ab initio molecular dynamics (AIMD) simulation was then applied topredict the conductivity of the targeted lithium silicates. The initialstructures were statically relaxed and were set to an initialtemperature of 100 K. The structures were then heated to targetedtemperatures (750-1150 K) at a constant rate by velocity scaling over atime period of 2 ps. The total time of AIMD simulations were in therange of 200 to 400 ps. A typical example of the calculated diffusivityas a function of temperature is shown in FIG. 1 . The Li⁺ diffusivity atdifferent temperatures from 750-1150 K follows an Arrhenius-typerelationship.

Applying equation (I) above the diffusivity at 300 K was determined andthen the conductivity may be determined using the link betweenconductivity and diffusivity of equation (II).

Accordingly, the first embodiment provides a solid-state lithium ionelectrolyte, comprising: a composite material of formula (I):Li_(y)(M1)_(x1) Si_(2-x2)(M2)_(x2)O₇  (I)

wherein x1 is a number from 0 to 6 inclusive of 0 and 6, x2 is a numberfrom 0 to 2, inclusive of 0 and 2, and y is a value such that thecomposite of formula (I) is charge neutral, wherein M1 is at least oneelement selected from the group of elements consisting of a group 1element, a group 2 element and a group 12 element, and M2 is at leastone element selected from the group of elements consisting of a group 13element, a group 14 element, and a group 15 element.

The composite materials of formula (I) have a crystal structurecomprising tetragonal unit cell (P42/m) with lattice parameters: a=7.72Å and c=4.88 Å. The lithium ion (Li⁺) conductivities of the solid statelithium ion electrolytes of formula (I) are at least 10⁻⁵ S/cm at 300Kand the activation energy of the composite of formula (I) is 0.4 eV orless.

In a special aspect of the first embodiment the composite of formula (I)may be a material of formula (Ia):Li₆Si₂O₇  (Ia).

The activation energy and room temperature conductivity determined forthe composite of formula 1(a) are shown in Table 1. FIG. 1 shows adiagram of the lattice structure for the composite of formula (Ia) andFIG. 2 shows a computer generated XRD analysis of the composite offormula (Ia) The Table of FIG. 3 lists the respective XRD peaks andtheir relative intensities compared to the peak of greatest intensity inthe XRD analysis. The major charateristic peaks are listed in Table 2.

TABLE 2 Major Peaks in XRD Analysis of Li₆Si₂O₇ Peak Position RelativeIntensity 21.55 24.8 24.47 52.16 25.82 100 31.76 21.87 36.84 31.47 41.3819.87 47.12 25.34

In a second embodiment, a solid-state lithium ion electrolyte,comprising: a composite material of formula (II) is provided:Li_(y)(M1)_(x1) Si_(2-x2)(M2)_(x2)Pb_(1-x3)(M3)_(x3)O₇  (II)

wherein x1 is a number from 0 to 10 inclusive of 0 and 10, x2 is anumber from 0 to 2, inclusive of 0 and 2, x3 is a number from 0 to 1,inclusive of 0 and 1, and y is a value such that the composite offormula (II) is charge neutral, M1 is at least one element selected fromthe group of elements consisting of a group 1 element, a group 2 elementand a group 12 element, M2 is at least one element selected from thegroup of elements consisting of a group 13 element, a group 14 element,and a group 15 element, M3 is at least one element selected from a group2 element, a group 12 element, a group 13 element, a group 14 elementand a group 15 element.

The composite materials of formula (II) have a crystal structurecomprising a monoclinic unit cell (C2/m) with lattice parameters:a=29.85 Å, b=6.11 Å and c=5.13 Å. The lithium ion (Li⁺) conductivitiesof the solid state lithium ion electrolytes of formula (II) are at least10⁻⁵ S/cm at 300K and the activation energy of the composite of formula(I) is 0.45 eV or less.

In a further aspect of the second embodiment, the composite of formula(II) comprises a crystal lattice structure having a monoclinic unitcell.

In a special aspect of the second embodiment the composite of formula(II) is a material of formula (IIa):Li₁₀Si₂PbO₁₀  ((IIa).

FIG. 4 shows a diagram of the lattice structure of the composite offormula (IIa) and FIG. 5 shows a computer generated XRD analysis of thecomposite of formula (IIa). The Table of FIG. 6 lists the respective XRDpeaks and their relative intensities compared to the peak of greatestintensity. Table 3 lists the major characteristic peaks.

TABLE 3 Major Peaks in XRD Analysis of Li₁₀Si₂PbO₁₀ Peak PositionRelative Intensity 6.00 100 14.82 39.20 19.51 14.04 22.96 15.65 29.1220.20 33.33 15.58 33.42 15.45

In a third embodiment, a solid-state lithium ion electrolyte,comprising:

a composite material of formula (III) is provided:Li_(y)(M1)_(x1)Si_(2-x2)(M2)_(x2)Al_(1-x3)(M3)_(x3)O₇  (III)

wherein x1 is from 0 to 1, inclusive of 0 and 1, x2 is from 0 to 1,inclusive of 0 and 1, x3 is from 0 to 1, inclusive of 0 and 1, and y isa value such that the composite of formula (III) is charge neutral, M1is at least one element selected from a group 1 element, a group 2element and a group 12 element, M2 is at least one element selected froma group 13 element, a group 14 element, and a group 15 element, and M3is at least one element selected from a group 3 element, a group 4element, a group 13 element, a group 14 element and a group 15 element.

The composite materials of formula (III) have a crystal structurecomprising a trigonal unit cell (R3) with lattice parameters: a=13.53 Åand c=9.04 Å. The lithium ion (Li⁺) conductivities of the solid statelithium ion electrolytes of formula (III) are at least 10⁻⁶ S/cm at 300Kand the activation energy of the composite of formula (I) is 0.40 eV orless.

In a special aspect of the third embodiment the composite of formula(III) is a material of formula (IIIa):LiAlSiO₄  (IIIa).

FIG. 7 shows a diagram of the lattice structure of the composite offormula (IIIa) and FIG. 8 shows the computer generated XRD analysis ofthe composite of formula (IIIa). The Table of FIG. 9 shows the peaks andrelative intensities compared to the peak of greatest intensity for theXRD analysis shown in FIG. 8 . Table 4 shows the major peaks in the XRDanalysis.

TABLE 4 Major Peaks in XRD Analysis of LiAlSiO₄ Peak Position RelativeIntensity 19.56 9.06 25.28 100 47.58 20.94 56.08 9.61 64.75 10.64

In a further special aspect of the third embodiment the composite offormula (III) is the material of formula (IIIb):Li_(1.33)Al_(1.33)Si_(0.67)O₄  (IIIb).

In a fourth embodiment a solid-state lithium ion electrolyte,comprising:

a composite material of formula (IV) is provided:Li_(y)(M1)_(x1)Si_(2-x2)(M2)_(x2)Be_(1-x3)(M3)_(x3)O₇  (IV)

wherein x1 is from 0 to 2, inclusive of 0 and 2, x2 is from 0 to 1,inclusive of 0 and 1, x3 is from 0 to 1, inclusive of 0 and 1, and y isa value such that the composite of formula (IV) is charge neutral, M1 isat least one element selected from the group of elements consisting of agroup 1 element, a group 2 element and a group 12 element, M2 is atleast one element selected from a group 13 element, a group 14 element,and a group 15 element, and M3 is at least one element selected from agroup 1 element, a group 2 element, a group 12 element and a group 13element.

The composite materials of formula (IV) have a crystal structurecomprising an orthorhombic unit cell (Pmnb) with lattice parameters:a=6.41 Å, b=10.52 Å and c=5.04 Å. The lithium ion (Li⁺) conductivitiesof the solid state lithium ion electrolytes of formula (IV) are at least10⁻⁶ S/cm at 300K and the activation energy of the composite of formula(I) is 0.4 eV or less.

In a special aspect of the fourth embodiment the composite of formula(IV) is a material of formula (IVa):Li₂BeSiO₄  (IVa).

FIG. 10 shows a diagram of the lattice structure of the composite offormula (IVa) and FIG. 11 shows a computer generated XRD analysis of thecomposite of formula (IVa). The Table of FIG. 12 lists the peaks andtheir relative intensities compared to the peak of greatest intensity ofthe XRD analysis of FIG. 11 . Table 5 shows the major peaks in the XRDanalysis.

TABLE 5 Major Peaks in XRD Analysis of Li₂BeSiO₄ Peak Position RelativeIntensity 23.09 80.7 23.85 60.01 23.99 62.79 26.20 24.78 34.42 100 36.3032.57 38.47 73.38 39.67 28.52 41.26 31.18 64.09 40.17

In a fifth embodiment, a solid-state lithium ion electrolyte,comprising: a composite material of formula (V) is provided:Li_(2.4)Zn_(4.4)Si_(5.2)O₁₆  (V).

The composite material of formula (V) has a crystal structure comprisinga monoclinic unit cell (Pmnb) with lattice parameters: a=6.4 Å, b=10.5 Åand c=5.0 Å. FIG. 13 shows a diagram of the lattice structure and FIG.14 shows a computer generated XRD analysis of composite of formula (V).The Table of FIG. 15 shows the peaks and their relative intensitiescompared to the peak of greatest intensity in the XRD analysis of FIG.14 . Table 6 shows the major peaks in the XRD analysis.

TABLE 6 Major Peaks in XRD Analysis of Li_(2.4)Zn_(4.4)Si_(5.2)O₁₆ PeakPosition Relative Intensity 21.86 69.54 22.44 65.65 24.45 60.49 27.8535.59 32.73 100 34.09 75.78 34.24 39.79 35.60 95.85 39.40 54.39 42.2033.36 57.55 35.15 60.16 59.58 68.48 38.12

The lithium ion (Li⁺) conductivities of the solid state lithium ionelectrolytes of formula (V) are at least 10⁻⁶ S/cm at 300K and theactivation energy of the composite of formula (V) is 0.5 eV or less.

TABLE 1 Activation energy and room temperature conductivity from AIMDsimulations. composition E_(a) (eV) σ (S/cm) Li₆Si₂O₇ 0.36 4 × 10⁻⁵ at300 K Li₁₀Si₂PbO₁₀ 0.42 6 × 10⁻⁵ at 300 K Li₂BeSiO₄ 0.39 7 × 10⁻⁶ at 300K LiAlSiO₄ 1.1 × 10−1 at 1150 K

Synthesis of the composite materials of the embodiments described abovemay be achieved by solid state reaction between stoichiometric amountsof selected precursor materials. Exemplary methods of solid statesynthesis are described for example in each of the following papers: i)Monatshefte für Chemie, 100, 295-303, 1969; ii) Journal of Solid StateChemistry, 128, 1997, 241; iii) Zeitschrift für Naturforschung B,50,1995, 1061; iv) Journal of Solid State Chemistry 130, 1997, 90; v)Journal of Alloys and Compounds, 645, 2015, S174; and vi) Z.Naturforsch. 5 Ib, 199652 5.

In further embodiments, the present application includes solid statelithium ion batteries containing the solid-state electrolytes describedabove. Solid-state batteries of these embodiments including metal-metalsolid-state batteries may have higher charge/discharge rate capabilityand higher power density than classical batteries and may have thepotential to provide high power and energy density.

Thus, in further embodiments, solid-state batteries comprising: ananode; a cathode; and a solid state lithium ion electrolyte according tothe embodiments described above, located between the anode and thecathode are provided.

The anode may be any anode structure conventionally employed in alithium ion battery. Generally such materials are capable of insertionand extraction of Li⁺ ions. Example anode active materials may includegraphite, hard carbon, lithium titanate (LTO), a tin/cobalt alloy andsilicon/carbon composites. In one aspect the anode may comprise acurrent collector and a coating of a lithium ion active material on thecurrent collector. Standard current collector materials include but arenot limited to aluminum, copper, nickel, stainless steel, carbon, carbonpaper and carbon cloth. In an aspect advantageously arranged with thesolid-state lithium ion conductive materials described in the first andsecond embodiments, the anode may be lithium metal or a lithium metalalloy, optionally coated on a current collector. In one aspect, theanode may be a sheet of lithium metal serving both as active materialand current collector.

The cathode structure may be any conventionally employed in lithium ionbatteries, including but not limited to composite lithium metal oxidessuch as, for example, lithium cobalt oxide (LiCoO₂), lithium manganeseoxide (LiMn₂O₄), lithium iron phosphate (LiFePO₄) and lithium nickelmanganese cobalt oxide. Other active cathode materials may also includeelemental sulfur and metal sulfide composites. The cathode may alsoinclude a current collector such as copper, aluminum and stainlesssteel.

In one aspect, the active cathode material may be a transition metal,preferably, silver or copper. A cathode based on such transition metalmay not include a current collector.

The above description is presented to enable a person skilled in the artto make and use the invention, and is provided in the context of aparticular application and its requirements. Various modifications tothe preferred embodiments will be readily apparent to those skilled inthe art, and the generic principles defined herein may be applied toother embodiments and applications without departing from the spirit andscope of the invention. Thus, this invention is not intended to belimited to the embodiments shown, but is to be accorded the widest scopeconsistent with the principles and features disclosed herein. In thisregard, certain embodiments within the invention may not show everybenefit of the invention, considered broadly.

The invention claimed is:
 1. A solid-state lithium ion electrolyte,comprising: a composite material of formula (I):Li_(y)(M1)_(x1)Si_(2-x2)(M2)_(x2)O₇  (I) wherein x1 is a number fromgreater than 0 to less than 6, x2 is a number from greater than 0 toless than 2, y is a value such that the composite of formula (I) ischarge neutral, M1 is at least one element selected from the group ofelements consisting of a group 1 element, a group 2 element and a group12 element, and M2 is at least one element selected from the group ofelements consisting of a group 13 element, a group 14 element, and agroup 15 element.
 2. The solid state lithium ion electrolyte accordingto claim 1, wherein a lithium ion (Li⁺) conductivity of the solid statelithium ion electrolyte is at least 10⁻⁵ S/cm at 300K.
 3. The solidstate lithium ion electrolyte according to claim 1, wherein anactivation energy of the composite of formula (I) is 0.4 eV or less. 4.The solid state lithium ion electrolyte according to claim 1, whereinthe composite of formula (I) comprises a crystal lattice structurehaving a tetragonal unit cell.
 5. The solid state lithium ionelectrolyte according to claim 1, wherein an XRD analysis of thecomposite comprises the following major peaks: Peak Position RelativeIntensity 21.55 24.8 24.47 52.16 25.82 100 31.76 21.87 36.84 31.47 41.3819.87 47.12 25.34.


6. A solid-state lithium ion electrolyte, comprising: a compositematerial of formula (II):Li_(y)(M1)_(x1)Si_(2-x2)d(M2)_(x2)Pb_(1-x3)(M3)_(x3)O₇  (II) wherein x1is a number from greater than 0 to less than 10, x2 is a number fromgreater than 0 to less than 2, x3 is a number from greater than 0 toless than 1, and y is a value such that the composite of formula (II) ischarge neutral, M1 is at least one element selected from the group ofelements consisting of a group 1 element, a group 2 element and a group12 element, M2 is at least one element selected from the group ofelements consisting of a group 13 element, a group 14 element, and agroup 15 element, M3 is at least one element selected from a group 2element, a group 12 element, a group 13 element, a group 14 element anda group 15 element.
 7. The solid state lithium ion electrolyte accordingto claim 6, wherein a lithium ion (Li⁺) conductivity of the solid statelithium ion electrolyte is at least 10⁻⁵ S/cm at 300K.
 8. The solidstate lithium ion electrolyte according to claim 6, wherein anactivation energy of the composite of formula (II) is 0.45 eV or less.9. The solid state lithium ion electrolyte according to claim 6, whereinthe composite of formula (II) comprises a crystal lattice structurehaving a monoclinic unit cell.
 10. A solid state lithium ionelectrolyte, comprising: a composite material of formula (IIa):Li₁₀Si₂PbO₁₀  (IIa).
 11. The solid state lithium ion electrolyteaccording to claim 10, wherein an XRD analysis of the compositecomprises the following major peaks: Peak Position Relative Intensity6.00 100 14.82 39.20 19.51 14.04 22.96 15.65 29.12 20.20 33.33 15.5833.42 15.45.


12. A solid-state lithium ion electrolyte, comprising: a compositematerial of formula (III):Li_(y)(M1)_(x1)Si_(2-x2)(M2)_(x2)Al_(1-x3)(M3)_(x3)O₇  (III) wherein x1is from greater than 0 to less than 1, x2 is from greater than 0 to lessthan 1, x3 is from greater than 0 to less than 1, y is a value such thatthe composite of formula (III) is charge neutral, M1 is at least oneelement selected from a group 1 element, a group 2 element and a group12 element, M2 is at least one element selected from a group 13 element,a group 14 element, and a group 15 element, and M3 is at least oneelement selected from a group 3 element, a group 4 element, a group 13element, a group 14 element and a group 15 element.
 13. The solid statelithium ion electrolyte according to claim 12, wherein a lithium ion(Li⁺) conductivity of the solid state lithium ion electrolyte is atleast 10⁻⁶ S/cm at 300K.
 14. The solid state lithium ion electrolyteaccording to claim 12, wherein an activation energy of the composite offormula (III) is 0.40 eV or less, and, the composite of formula (III)comprises a crystal lattice structure having a trigonal unit cell. 15.The solid state lithium ion electrolyte according to claim 12, whereinan XRD analysis of the composite comprises the following major peaks:Peak Position Relative Intensity 19.56 9.06 25.28 100 47.58 20.94 56.089.61 64.75 10.64.


16. A solid-state lithium ion electrolyte, comprising: a compositematerial of formula (IV):Li_(y)(M1)_(x1) Si_(2-x2)(M2)_(x2)Be_(1-x3)(M3)_(x3)O₇  (IV) wherein x1is from greater than 0 to less than 2, x2 is from greater than 0 to lessthan 1, x3 is from greater than 0 to less than 1, y is a value such thatthe composite of formula (IV) is charge neutral, M1 is at least oneelement selected from the group of elements consisting of a group 1element, a group 2 element and a group 12 element, M2 is at least oneelement selected from a group 13 element, a group 14 element, and agroup 15 element, and M3 is at least one element selected from a group 1element, a group 2 element, a group 12 element and a group 13 element.17. The solid state lithium ion electrolyte according to claim 16,wherein a lithium ion (Li⁺) conductivity of the solid state lithium ionelectrolyte is at least 10⁻⁶ S/cm at 300K.
 18. The solid state lithiumion electrolyte according to claim 16, wherein an activation energy ofthe composite of formula (I) is 0.40 eV or less.
 19. The solid statelithium ion electrolyte according to claim 16, wherein the composite offormula (IV) comprises a crystal lattice structure having anorthorhombic unit cell.
 20. The solid state lithium ion electrolyteaccording to claim 16, wherein an XRD analysis of the compositecomprises the following major peaks: Peak Position Relative Intensity23.09 80.7 23.85 60.01 23.99 62.79 26.20 24.78 34.42 100 36.30 32.5738.47 73.38 39.67 28.52 41.26 31.18 64.09 40.17.